Approach:
Carcasses will be sampled from two large-scale, fed-beef packing plants representing geographical differences in cattle populations. At each plant, carcasses will be sampled from Certified Angus Beef (i.e., Modest and Moderate marbling scores), Choice Angus (i.e., Small marbling score), and Select Angus (i.e., Slight marbling score) product lines. Within each plant, 30 head will sampled for each product line. Thus, the total number of carcasses sampled will be 180 (2 plants × 3 marbling levels × 30 carcasses/marbling level/plant = 180 carcasses).
At 6 d postmortem, each muscle will be sliced into 28-mm thick steaks. Steaks will be blocked by location within cuts and assigned to aging times of 7, 14, 21, and 35 d postmortem. Steaks will be aged under conventional refrigerated conditions (1°C). At the appropriate day postmortem, fresh (never frozen) steaks will be cooked and SSF will be determined. The total number of steaks to be evaluated will be (2 plants × 3 marbling levels × 30 carcasses/marbling level/plant × 3 muscles/carcass × 4 aging periods/muscle = 2,160 steaks).